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Ipv4 Subnet Calculator Validator🔒 100% local
Calculate IPv4 subnet ranges. Privacy-first, no server uploads, no tracking.
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One address per run, with or without a prefix, and the page returns the masked network, broadcast, netmask, wildcard, first and last usable host, host count, classful class, RFC 1918 status, and both the netmask and the network in binary. A bare address is treated as /24. The arithmetic is plain bit shifting on the mantissa, so nothing about your network is sent anywhere.
How to use it
- Type a single CIDR, for example 192.168.1.0/24.
- Press Process; leaving the slash off assumes /24, so 172.16.5.4 is read as 172.16.5.4/24.
- Copy Output for the whole block, binary rows included, when you need it in a ticket or a firewall note.
Worked example
192.168.1.0/24becomesInput: 192.168.1.0/24
Network: 192.168.1.0
Broadcast: 192.168.1.255
Netmask: 255.255.255.0 (24 bits)
Wildcard: 0.0.0.255
First host: 192.168.1.1
Last host: 192.168.1.254
Hosts: 254
IP class: C
Private: yes (RFC 1918)
Binary netmask: 11111111.11111111.11111111.00000000
Binary network: 11000000.10101000.00000001.00000000Classic /24: 254 usable addresses after network and broadcast are removed.
10.0.0.0/31becomesInput: 10.0.0.0/31
Network: 10.0.0.0
Broadcast: 10.0.0.1
Netmask: 255.255.255.254 (31 bits)
Wildcard: 0.0.0.1
First host: 10.0.0.0
Last host: 10.0.0.1
Hosts: 2 (RFC 3021 point-to-point)
IP class: A
Private: yes (RFC 1918)
Binary netmask: 11111111.11111111.11111111.11111110
Binary network: 00001010.00000000.00000000.00000000The /31 branch follows RFC 3021: both addresses are shown as usable and labelled point-to-point instead of the usual minus-two count.
When to use it
- You are sizing a new subnet and want the host count and broadcast address for a prefix length.
- You need the wildcard mask for an ACL or a firewall rule rather than the netmask.
- You are checking whether an address range is private before putting it in a document.
What it does not do
- One CIDR per run. A second address or a newline fails the single-line pattern instead of producing a table.
- The private check runs on the text you typed rather than on the masked network, so a public address inside an otherwise private block is still labelled public.
- Only RFC 1918 ranges count as private - carrier-grade NAT (100.64.0.0/10) and link-local (169.254.0.0/16) are both reported as public.
- The IP class column is the 1981 classful label and has no bearing on routing today; a /0 lookup reports 4,294,967,294 usable addresses, which is arithmetically right but rarely a useful answer.